Alpha-Absorption Lab Homework: Determining Geiger Counter Window Thickness

[zheng89120]

Homework Statement

"Place the geiger counter in the plastic ²⁴¹Am alpha-source enclosure. (basically, a distance of air separates the geiger counter window and the ²⁴¹Am source) Re-apply the voltage and determine the counting rate. Repeat with various numbers of very thin mylar sheets on top of the source. The alpha particles of ²⁴¹Am have an energy of 5.48 MeV. This information and a graph of counting rate versus absorber thickness may be used to determine the combined thickness of the Geiger counter window and any portective coating on the surface. To do this you will have to estimate the thickness of air between the source and the holder. A table of the rate of energy loss of alpha-particles of a variety of energies and materials is appended. It lists the energy per nucleon and the energy of alpha-particles."

Homework Equations

Nuclear physics knowledge and error analysis

The Attempt at a Solution

thickness of glass x stopping power of glass = Sigma (thickness x stopping power of the Am)? - thickness of air x stopping power of the air -thickness of mylar x stopping power of Mylar?

Ok I think I'm suppose to use the Energy/(mass/Area) for stopping power, but what what am I suppose write for Sigma (thickness x stopping power of Am)?

 

[zheng89120]

YES YES YES, I figured it out after a lot of thinking, but only a little dimensional analysis:

Density glass x Length glass x Stopping power glass = Energy Am – Density N x Length Air x Stopping power N – Density O x Length Air x Stopping power O

(Length in cm, Stopping power in mg/cm2, Density in mg/cm3)

 

[zheng89120]

Now I just need to know stopping power of glass, anyone??